Portable oxygen concentrator



FIG. 1 is a front view of our portable oxygen concentrator showing our new design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a rear view thereof; and,

FIG. 5 is a side view thereof, the opposite side being a mirror image.

The broken lines in FIGS. 1, 2, 4 and 5 are included for the purpose of illustrating portions of the portable oxygen concentrator that form no part of the claimed design. 

The ornamental design for a portable oxygen concentrator, as shown and described. 